Practical security and storage enclosure mechanisms for open bed vehicles, such as pickup trucks, preferably incorporate some form of extensible and retractable cover arrangement that facilitates access to the truck bed, while still providing a mechanically rigid assembly that protects the contents of the bed when fully closed. To this end there have been proposed a variety of vehicle bed enclosure apparatuses which employ sectional covers that are designed to be foldable or rollable across the top of the vehicle bed between their stowed and fully deployed (enclosing) configurations.
(For an overview of typical examples of these types of vehicle body (e.g. truck bed) enclosure mechanisms, attention may be directed to the U.S. Pat. Nos. to Hull et al, 3,986,749, Forsberg, 3,820,840 and Cross, 3,649,072 (which show foldable arrangements) and the U.S. Pat. Nos. to Renquist 2,771,319, Comisac, 3,472,548 and Campbell 4,252,362 (describing sectional roll-up configurations). In addition to these foldable and roll-up sectional vehicle bed enclosures, the (Patent) literature describes non-retractable (e.g. non-foldable) sectional vehicle bed enclosures, such as those disclosed in the U.S. Pat. Nos. to Deshores 3,762,763, Hallock et al, 3,165,352, Albrecht et al 4,199,188, Lutgen 3,342,523 and Fellenstein 3,829,151, and roll-up pliable material covers (e.g. sand and gravel covers) such as those detailed in the U.S. Pat. Nos. to Thompson et al 3,366,414, Schultz 2,757,042, McKeon 4,138,154, Johnsen 4,212,492, Dimmer et al, 4,302,043, Petretti 4,082,347 and Rosenvold 4,234,224. From a practical standpoint, however, these configurations are incapable of operating as practical extensible and retractable security enclosures.)
For the most part foldable cover arrangements are large sized, due to both the widths of the folds of the cover and the resulting volume of stowage area required to accommodate the cover in its folded condition. Rollable arrangements of interlinked sections (slats), on the other hand, are designed to provide a more compact stowage configuration (as the sections of the cover are wrapped around a (rotatable) bar or axle) and therefore more adaptable to today's smaller light utility vehicles. Disadvantageously, however, conventional rollable sectional vehicle bed enclosures have a tendency to jam in the vicinity of the stowage box as the slats of the cover are sequentially unrolled from their wrapped, stowed condition.
More particularly, with reference to FIG. 1, there is shown a diagrammatic side view of a rollable vehicle bed enclosure 10 formed of a plurality of interlinked parallel slats 11 that are arranged to be unwound from a rotatable stowage bar 13 and slidable along a pair of guide tracks or channels 12 affixed to the sidewalls of a vehicle bed. The respective slats 11 are unrolled from their rolled-up condition, shown at 14, by (motor-driven) rotation (counter-clockwise as shown in FIG. 1) of stowage bar 13, causing the slats to be effectively pushed out from the roll 14 and into guide channel 12. Due to the influence of gravity, however, which assists in moving the slats off the stowage bar 13 into their extended position, the slats tend to fall away from the roll 14 in an initially vertical direction causing the cover to droop slightly upstream of the entry point of the slats into the channel 12. Consequently, as the stowage bar 13 continues to rotate and push the slats outwardly and toward the channel 12, the slats become bunched together and jam at the entrance to the channel, thereby inhibiting proper operation of the enclosure.